1. Field of the Invention
The invention relates to a changer apparatus for information discs, comprising a stacking unit for stacking at least two holder compartments, adapted to hold one information disc each, in at least two stacking positions, the holder compartments being coupled to at least one spindle having a screwthread and the holder compartments being movable in a vertical direction by rotation of the spindles, an upper stacking zone and a lower stacking zone of the stacking unit being provided for stacking the holder compartments, and the changer apparatus having a play position for reading information stored on the information discs and/or writing information on the information discs.
Herein, a screwthread is to be understood to mean a helical path which can have different pitches.
2. Description of the Related Art
Such a changer apparatus for information discs is known from JP 6-131793 of Clarion Co. Ltd. This known changer apparatus comprises four threaded spindles with external screwthread. A plurality of holder compartments has been provided for holding one information disc each, which holder compartments each have four bores with internal screwthreads in which the external screwthreads of the threaded spindles engage. The external screwthreads of the threaded spindles have a small pitch in the axial direction in the upper and the lower stacking zone and a large pitch in the intermediate zone between the upper and the lower stroking zone. When the threaded spindles are rotated the holder compartments are moved in the vertical direction, the intermediate zone being free from holder compartments to allow the individual information discs to be read. A read unit is arranged on a pivotal arm and for reading it is pivoted into the intermediate zone of the stacking unit.
Such a read unit arranged on a pivotal arm has the disadvantage that it is susceptible to external vibrations and shocks.
This is of particular importance when the changer apparatus is used in motor vehicles.
It is an object of the invention to provide improved changer apparatus of the type defined in the opening paragraph.
According to the invention this object is achieved in that a loading position is provided in a central zone of the stacking unit between the upper and the lower stacking zone, into which loading position one of the holder compartments is each time movable by rotation of the spindles, and transport means are provided, which are adapted to move the information disc from the holder compartment, which is in the loading position, into the play position and into the eject position in which the information disc can be removed from the apparatus, the play position being arranged between the eject position and the loading position.
To load an information disc the information disc is first brought into the eject position by hand by a user. This information disc is then moved into a holder compartment of the stacking unit, which holder compartment is in the loading position, with the aid of the transport means. By rotation of the spindles this holder compartment together with the information disc is then moved into one of the stacking positions in the lower or the upper stacking zone.
For the transport of an information disc from the stacking position into the play position this information disc together with the holder compartment is moved into the loading position by rotation of the spindles. From this loading position the information disc is then removed from the holder compartment with the aid of the transport means and is brought into the play position. The transport means are also adapted to move the information disc into the eject position. The play position is situated between the eject position and the loading position.
Such a changer apparatus has the advantage that a read/write unit adapted to read information stored on the information discs and/or to write information on the information discs can be isolated more simply from external disturbances and vibrations.
This is particularly advantageous in the case of changer apparatuses intended for use in motor vehicles.
A further advantageous embodiment of the invention is characterized in that in the axial direction of the spindles the central zone has spacing zones at both sides of the loading position, which spacing zones define an axial spacing between the holder compartment in its loading position and the axially adjacent holder compartments in their stacking positions.
The spacing zones arranged at both sides of the loading position, i.e. above and below the loading position, provide room for the transport means and allow said means to move an information disc into a holder compartment in the loading position and an information disc out of a holder compartment in the loading position without the other holder compartments being touched.
A further advantageous embodiment of the invention is characterized in that the average screwthread pitch of the spindles in the loading position is smaller than the average screwthread pitch in the upper and the lower stacking zone.
The screwthread pitch of the spindles in the upper and the lower stacking zone is basically determined by the height of the holder compartments. For a trouble-free and reliable cooperation of the transport means with the information disc which is in the loading position it is advantageous that the axial orientation of the information disc in the loading position is defined as accurately as possible. Therefore, it is favorable to choose the average screwthread pitch of the spindles in the loading position smaller than the average screwthread pitch in the upper and the lower stacking zone. The effect of tolerances of the angle of rotation of the threaded spindles on the axial position of the holder compartments and of the information disc in the loading position decreases as the average screwthread pitch of the spindles in the loading position becomes smaller. Therefore, it is particularly advantageous that the screwthread pitch of the spindles in the loading position is substantially zero. As a result of this, the individual holder compartments can be moved into the loading position very accurately as regards the axial height and in a reproducible manner. Tolerances as regards the angle of rotation of the threaded spindles, for example owing to overshoot of the drive system of the threaded spindles or step tolerances of a stepper motor which drives the threaded spindles have no or only a minimal influence on the axial height of the loading position.
A further advantageous embodiment of the invention is characterized in that the average screwthread pitch in the spacing zones is greater than the average screwthread pitch in the upper and the lower stacking zone.
When the average screwthread pitch in the spacing zones is increased the axial distance between the holder compartment in the loading position and the adjacent holder compartments in the lower and the upper stacking zone increases and the transport means have more room for access to the information disc.
A further advantageous embodiment of the invention is characterized in that there is provided a lower and an upper guide pin for guiding the information discs into the holder compartments of the stacking unit, which guide pins are engageable into the center holes of the information discs from above and from below, respectively.
Such an arrangement prevents the information discs from radially slipping out of the holder compartments during the axial movement of the holder compartments. The radial positions of the information discs inside the stacking unit are defined exactly by the guide pins. For the transport of an information disc out of or into a holder compartment which is in the loading position the upper and the lower guide pin are moved up and down, respectively.
A further advantageous embodiment of the invention is characterized in that a read/write unit for reading information stored on the information discs and/or writing information on the information discs is movably supported on a chassis plate of the apparatus.
As a result of this, the available mounting space can be utilized in an optimum manner. This is particularly important in the case of automotive uses because the available mounting space is then very limited.
A further advantageous embodiment of the invention is characterized in that the read/write unit comprises a base plate and a laser mounting plate, the base plate and the laser mounting plate are coupled by means of dampers, the base plate is slidably mounted on the chassis plate, and the laser mounting plate carries a clamping device for clamping the information disc in the play position and an optical unit for reading information stored on the information disc.
Such an arrangement provides a very effective isolation of the read/write unit from external vibrations and shocks.